CORONARY VASOMOTION IN CORONARY-ARTERY DI SEASE - RELEVANCE OF EPICARDIAL AND MICROCIRCULATORY VESSELS FOR MYOCARDIAL PERFUSION

The most important function of the coronary vasculature is the effecti ve regulation of coronary blood flow according to the metabolic needs of the myocardium. Under physiological conditions, coronary blood flow is regulated by a balance of vasoconstricting and -dilating component s which can be differentiated with regard to the site (macro-vs. micro circulation), compartment (endothelium vs. vascular smooth muscle), an d mechanism of action (receptor dependent vs. independent). This balan ce includes on the one hand the ability of the coronary circulation to maintain a relatively constant blood flow at any given oxygen demand irrespective of perfusion pressure (coronary autoregulation). On the o ther hand, coronary blood flow can be increased rapidly and effectivel y several-fold when myocardial oxygen demand increases. Previous inves tigations have demonstrated that the coronary endothelium plays a key role in the development of arteriosclerotic vascular lesions. In the t ime course of arteriosclerosis, functional alterations in endothelium dependent vasodilatation alterations are already present before angiog raphically demonstrable morphologic lesions. In the present manuscript , the diagnostic methods used to assess clinically the coronary macro- and microcirculation with regard to endothelium and smooth muscle dep endent vasomotion are reviewed. In addition, present pharmacotherapeut ic strategies to improve myocardial perfusion in coronary artery disea se are discussed.